The present embodiments relate to shear speed imaging. The shear speed of tissue may be diagnostically useful, so ultrasound is used to estimate the shear speed of a patient's tissue. By transmitting an acoustic radiation force impulse (ARFI), a shear wave is generated at the ARFI focus. Ultrasound scanning monitors the propagation of the shear wave. The time-to-peak displacement at a distance from the origin of the shear wave is used to determine the velocity of the shear wave in the tissue.
Penetration is a problem in shear wave speed imaging. The attenuation of the acoustic push pulse (i.e., ARFI) and the safety limits for ultrasound power result in weaker push pulses at deeper depths. The signal-to-noise ratio may result in failure to obtain an accurate velocity estimate. The estimated shear speed values become unreliable. Even at shallower depths, the signal-to-noise ratio may result in less reliability in the estimate, especially for stiffer tissue (e.g., fibrotic liver).